The present invention relates to a fuel cap (hereinafter simply called cap) attached to a filler neck of a fuel tank of an automobile and, particularly, relates to a fuel cap having a negative pressure valve permitting air to flow from the outside of a fuel tank to the inside thereof at the time of lowering of the inner pressure of the fuel tank to prevent the inner pressure of the fuel tank from lowering further.
A cap of this type is described in Japanese Utility Model Unexamined Publication No. Sho-63-86481 for preventing dust or the like mixed in flowing-in air at the time of operation of the valve from depositing on the negative pressure valve.
In the cap described in the aforementioned Publication, a dust proof plate is arranged in an air passage up to the negative pressure valve to alter the flow of air and make the dust mixed in the air fall, to thereby obtain an effect of being dust proof.
In the cap described in the above Publication, however, there is still room for improvement in the durability of the dust proof effect, because the space of the place where the fallen dust can deposit is small.